Kiln



Noir. 8, 19378. M. VOGEL-JORGENSEN 2,135,174

KILN

Filed July 23, 1937 gjm ms"mf ATTORNEYS Patented Nov. 8, 1938 KILN Mikael Vogel-Jorgensen, Frederiksberg, near Copenhagen, Denmark, assignor to F.

Smidth & Co., New York, N. Y., a corporation of New Jersey Application July 23, 1937, Serial No. 155,151 In Great Britain August 6, 1936 9 claims. (ci. 263-32) This invention relates to rotary kilns heated by a llame directed axially along the kiln from the outlet end in countercurrent to the iiow of material through the kiln and supported by secondary air for combustion admitted through one or more openings. More particularly, the invention is concerned with a novel kiln of the type referred to which includes means by which the admission of secondary air into the kiln is controlled and the ingress of air in proximity to the material in the kiln is prevented or reduced.

In rotary kilns in which combustion is supported by the admission of secondary air, it is important to keep at a minimum the amount of dust arising Within the kiln during operation, since the presence of dust in the burning zone impairs the vision of the operator who controls the supply of fuel and material to the kiln. In-

certain industries, the nature of the raw materials being burned is such as to aggravate the dust conditions within the kiln, an example of such material being alumina, which, when it reaches the burning zone, contains very ne particles readily picked up by the secondary air. The iiow of the air through the kiln may carry such fine particles back to the outlet through which the waste gases issue, and the likelihood of such entrainment is increased when the secondary air is admitted into the kiln in such a way as to ow close to the surface of the material in the kiln.

The present invention is, accordingly, directed to the provision of a kiln in which entrainment of fine material by the secondary air is avoided or minimized, and for this purpose, the kiln is provided with means, preferably operating automatically as the kiln rotates, to control the admission of secondary air and to admit such air only at a distance from the material. The invention may be embodied in rotary kilns of various kinds, but since it aiords special advantages in connection with kilns having a series of cooling drums or tubes disposed in a planetary arrangement at the outlet end, a kiln of this specic type, in which the invention is employed, will be illustrated and described in detail for purposes of explanation. It is to be understood, however. and Will be apparent that the utility of the invention is not limited to rotary kilns of any particular construction.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which Figure l is a longitudinal sectional view, with parts shown in elevation, of a new kiln provided with cooling tubes;

Figure 2 is a diagrammatic perspective view showing the mode of operation of the air control mechanism employed in the kiln of Figure l;

Figure 3 is'a fragmentary perspective view of a modified control means: and

Figure 4 is a diagrammatic end elevation of another form of the control means.

In the construction illustrated in Figure 1, the kiln I0 is supported in the usual manner by tires II resting on rollers I2 and rotated by the 4usual driving means, and the shell of the kiln has the customary refractory lining I3 which is of increased thickness in the burning zone, as indicated at I4. A plurality of openings I5 are formed in the kiln beyond the ring I4 to permit the discharge of the smaller pieces or lumps of material which pass through the openings into cooling drums or tubes I6. The pieces of material which are too large to enter the openings I5 pass into an extension I1 of the kiln, the lining of which is thickened to provide a ring I8 which retains such pieces until it is desired to remove them. The end of the kiln is provided with a closing hood I9 through which a burner 20 projects, the burner serving to direct a flame axially into the kiln, and the hood is provided with a door 2| through which the larger pieces of material may be removed. The kiln is provided with the usual peep holes and other features commonly employed in kilns of this construction.

The cooling tubes are of the usual construction and are provided at their ends 22 with closures having openings 23 through which material is discharged and air admitted. The openings are so placed that they lie near the bottoms of the tubes when the latter are in lowermost position, and pivotally mounted on the closure of each tube is a damper 24 of sector shape and of suicient size to close the opening. During rotation of the kiln, the dampers swing freely n their pivots and alternately open and close the openings 23, the arrangement being such that ingress of air through each tube and into the kiln is prevented at a time when the passage I5 leading from the tube into the kiln lies beneath the material within the kiln or close to the surface of the material.

In some instances, it may be desirable to vary the timing of the opening and closing of the dampers, and for this purpose, the constructions shown in Figures 3 and 4 may be employed. In the Figure 3 construction, each damper is provided With a ring 25 which extends about the end of the tube I6 and a weight 21 is adjustably mounted on the ring. By shifting the weight along the ring to different positions, the action of the damper in opening and closing its opening 23 may be varied as desired. In the construction illustrated, the tube I6 is provided with an air inlet opening 23 at its end, and another opening 28 through its wall through which the cooled material may be discharged. The damper 2l is,

accordingly, provided with an extension 29 along the outside of the tube, which serves to control the opening 28. With the construction described,

the admission of air is not reduced by the outflow' of material during the discharging period, but ,l

both openings are closed at the same time to prevent a dust condition from occurring in the kiln.

In the Figure 4 construction, the dampers 30 pivotally mounted on the ends of the tubes to control the openings 3i are provided with extensions 33 carrying rollers 3l, which engage a cam rail 35, mounted adjacent to the series of dampers. As the kiln rotates, the rail swings the dampers to open position and holds them in open position longer than would be the case il the dampers were controlled by gravity alone. This arrangement ls permissible in the kiln illustrated by reason of the slope of the material, as indicated at 36, and the use of the cam means insures a greater supply of secondary air than in the constructions inwhich the dampers are operated by gravity only.

I claim:

1. The combination with a rotary kiln having an end at which the material discharges, oi' a burner for directing a flame axially into the kiln at said end, the kiln having a plurality of openings adjacent said end for the admission oi' air for combustion, and means operating automatically as the kiln rotates to permit the ingress of air through said openings during the major part of the rotation of the kiln and to prevent admission of air in proximity to the material Within the kiln.

2. The combination with a rotary kiln having an end at which the material discharges, of a burner for directing a ame axially into the kiln at said end, the kiln having a plurality of openings adjacent said end for the admission of air for combustion, and dampers for the individual openings operating automatically as the kiln rotates to keep said openings unclosed during the major part of the rotation of the kiln to permit the ingress of air therethrough and to close said openings during the remaining part of the rotation of the kiln to prevent admission of air to the` kiln in proximity to the material within the kiln.

3. The combination with a, rotary kiln having an end at which the material discharges, of a burner for directinga flame axially into the kiln at said end, the kiln having a series of openings adjacent said end for admission of air for combustion, and pivotally mounted dampers for the individual openings moving as the kiln rotates to keep said openings unclosed during the major part of the rotation of the kiln to permit the ingress of air therethrough and to close said openings during the remaining part of the rotation of the kiln to prevent ingress of air through the openings in proximity to the material in the kiln.

4. The combination with a rotary kiln having an end at which the material discharges, oi a burner for directing a flame axially into the kiln at said end, the kiln having a series of openings adjacent said end for admission of air for combustion, movable dampers i'or the individual openings, and controlling means for the dampers operating as the kiln rotates to cause the dampers to prevent ingress of air in proximity to the material in the kiln and to cause the dampers aiscnn to permit ingress of air during the major part of the rotation of the kiln.

5. The combination with a rotary kiln, 0i.' a plurality of' cooling tubes arranged about the kiln at the discharge end thereof in a circumferential series and receiving material discharging from the kiln, a burner for directing a name axially into the kiln at said discharge end, air for com.- bustion being admitted into the kiln through said tubes, and means associated with the tubes to permit the ingress of air through the tubes during the major part of the rotation of the kiln and to prevent admission of air to the kiln in proximity to the material within the kun.

6. The combination with a rotary kiln having an end at which the material discharges, of a burner for directing a flame axially into the kiln at said end, a plurality of tubes adjacent said end receiving material from the kiln and admitting air for combustion into the kiln, and means for controlling the admission of air into the kiln through said tubes including dampers for the lndiv'idual tubes mounted for free movement as the kiln rotates and preventing ingress of air into the kiln in proximity to the material therein.

7. The combination with a rotary kiln having an end at which the material discharges, of a burner directing a` iiame axially into the kiln at said end, a plurality of cooling tubes mounted adjacent said end and in communication with the interior of the kiln to receive material discharging therefrom and to admit airior combustion, each tube having a discharge opening, dampers mounted on the tubes to control admission of air through the tube discharge openings, and cam means mounted adjacent the kiln and controlling the dampers to permit ingress of air through said openings during the major part of the rotation of the kiln, said dampers preventing ingress of air into the kiln in proximity to the material therein.

8. The combination with a rotary kiln having an end at which the material discharges, of a burner directing a flame axially into the kiln at said end, a plurality of cooling tubes mounted adjacent said end and in communication with the interior of the kiln to receive material discharging therefrom and to admit air for combustion, each tube having an opening at its end and an opening in its wall for discharge of material and admission of air, and dampers for the individual tubes for controlling both openings thereof, said dampers being moved automatically as the kiln rotates to prevent ingress of air into the kiln in proximity to the material therein.

9. The combination of a rotary kiln having an end at which the material discharges, of a burner for directing a flame axially into the kiln at said end, the kiln having a plurality of openings adjacent said end through which air may be admitted and supplied to the interior of the kiln at a plurality of circumferentially spaced delivery points, and means operating automatically as the kiln rotates to close each of said openings to prevent the delivery of air at the corresponding delivery point in the kiln during the time that such delivery point lies beneath the material within the kiln or close to the surface of the material and to keep each oi' said openings unclosed during the time that the corresponding delivery point traverses the remaining part oi' its travel. i

MIKAEL VQGEL-JORGENSEN. 

